Chemical Profiling and Differential Analysis of Whiskies Using Orbitrap GC-MS

Significance of the Topic

This study addresses the need for robust chemical profiling of whisky to ensure product authenticity, detect adulteration and maintain consistent quality. Given the high value and global demand for premium spirits, reliable analytical methods are crucial for brand protection, regulatory compliance and quality control across distilleries and regions.

Objectives and Study Overview

The work aimed to apply an untargeted chemometric workflow using high-resolution Orbitrap GC-MS to:

• Characterize volatile and semi-volatile compounds in whiskies of diverse origins, types and ages
• Detect compositional differences via statistical analysis
• Identify marker compounds responsible for variation between samples

Methodology

Nine whisky samples (various Scotch single malts and a Kentucky bourbon) were extracted by liquid–liquid partitioning into ethyl acetate, concentrated under nitrogen and reconstituted. A pooled composite sample and a solvent blank were included. Each extract was injected in quadruplicate in randomized order. Data acquisition used full-scan electron ionization (EI) and positive chemical ionization (PCI) to collect accurate mass spectra over m/z 50–600. Chromatograms were aligned, deconvoluted and subjected to principal component analysis (PCA) using SIEVE 2.2. Compound identification combined spectral library matching with accurate mass filtering in TraceFinder and structural confirmation via Mass Frontier.

Used Instrumentation

• Q Exactive GC Hybrid Quadrupole-Orbitrap Mass Spectrometer
• Thermo Scientific TRACE 1310 GC with TG-5SilMS capillary column
• TriPlus RSH autosampler
• Acquisition resolution: 60,000 FWHM at m/z 200; EI at 70 eV; PCI with methane reagent gas

Principal Results and Discussion

PCA clearly separated Scotch malts by region and age and distinguished bourbon from malt whiskies. Marker discovery highlighted elevated trans β-ionone in bourbon, consistent with corn-derived β-carotene breakdown. Another marker, 3-carboxy-4-methyl-5-propyl-2-furanpropanoic acid, was identified by coupling PCI-based formula proposals with EI fragment validation at sub-1 ppm mass error. Within a single distillery, three maturations (12, 18 years and no-age-statement in different casks) showed distinct profiles; elevated hydroxymethylfurfural in sherry and bourbon cask-aged whisky reflected wood sugar dehydration.

Benefits and Practical Applications

• Rapid untargeted profiling supports authenticity testing and counterfeit detection
• High-resolution data enable confident compound identification, even without library matches
• Chemometric workflows allow batch comparison and monitoring of production consistency

Future Trends and Opportunities

Advances in high-resolution GC-MS, automated spectral deconvolution and machine-learning-driven chemometrics will further enhance trace-level detection of adulterants, enable geographical origin verification and support dynamic quality surveillance. Integration with multidimensional separations and complementary ionization modes promises deeper molecular coverage.

Conclusion

The demonstrated Orbitrap GC-MS workflow delivers comprehensive, high-confidence chemical profiling of complex spirit matrices. Combining accurate-mass full-scan acquisition with statistical analysis and structural elucidation provides a powerful platform for quality control, authenticity verification and product differentiation in the whisky industry.

Reference

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